The purpose of this study is to find the diagnostic performance of biomarkers of myocardial necrosis in a study that includes all patients who are evaluated in the emergency department (ED) for acute cardiac ischemia (ACI). Unlike previous studies which only look at patient who are hospitalized, this study will look at patients who are not hospitalized to there by allow accurate assessment of the false negative diagnostic rate for all patients evaluated for ACI in the ED. All patients enrolled in the study will have a tube of blood drawn at zero and three hours on which multiple biomarker tests will be performed. The true final diagnosis will be determined on each patient based on ECG done in the ED and at 24 hours; and standard CK tests. This confirmed diagnosis will be determined on all patients (whether admitted to the hospital or sent directly home from the ED). The formulation of a databank of blood samples that will contain various biomarker test results (troponin, CK, myoglobin, etc) and the associated ""true"" diagnosis of each study subject will also allow us to determine the usefulness of these tests as predictors of ischemia when used in the ED. Additionally, as new assays are developed they will be tested on the databank samples and evaluation of the new tests will be easily assessed.